The present invention relates to an automatic transaxle, and more particularly to an improvement in construction of an automatic transaxle.
A 440-T4 automatic transaxle is shown in FIG. 1 of a publication entitled "Oldsmobile Chassis Service Manual" issued in 1984 by General Motors in the United States of America. As readily understood from a fragmentary view shown in FIG. 4, this known automatic transaxle comprises a torque converter 80 including an impeller 80a, a turbine 80b, and a stator 80c, a rotary motion transmitting unit including a driver chain sprocket 81 coaxially arranged with the impeller 80a, a follower chain sprocket 87, and a chain 88 drivingly interconnecting the driver and follower chain sprockets 81 and 87, a pump 82 in driving connection with the impeller 80a. The impeller 80a is drivingly connected to an engine output shaft, not shown, by a converter cover 80d. The stator 80c is drivingly connected to an outer race of a one-way clutch (an overrunning clutch) 80e whose inner race is drivingly connected to a reaction shaft 91 bolted to a casing 92. This reaction shaft 91, extending through a sleeve 80f of the impeller 80a, rotatably supports the driver sprocket 81 via ball bearing 90. A hollow input shaft 83, coaxially arranged with the impeller 80a, has one end drivingly connected to the turbine 80b. Splined to the input shaft 83 is the driver chain sprocket 81. Thus, a rotary motion is transmitted from the turbine 80b to the driver chain sprocket 81. This rotary motion is transmitted further to the follower chain sprocket 87 by the chain 88. The follower sprocket 87 is splined to a hollow gear box input shaft 86 and rotatably supported via bearing 93 by a follower sprocket support 94 fixed relative to the casing 92. Thus, the rotary motion is transmitted to the gear box input shaft 86. Extending through the gear box input shaft 86 is an output shaft 89. The pump 82 has a pump housing including a pump body 82a and a pump cover 82b. The pump cover and body 82b and 82a are bolted to a control valve assembly 84 which, in turn, is bolted to the casing 92. In order to drive the pump 82, a pump shaft 85 extends through the hollow input shaft 83. The pump shaft 85 has one end splined to the converter cover 80d in driving connection with the impeller 80a and an opposite end splined to the pump 82 at its pump rotor.
In this known automatic transaxle, an axial dimension of an arrangement of component parts around the input shaft can not be compressed since the driver sprocket and the control valve assembly are arranged between the torque converter and the pump. Besides, the input shaft is complicated and cannot be strengthened since the pump shaft extends through the input shaft and a bearing arrangement is to be provided within the input shaft. Since the pump shaft extends through the input shaft which in turn extends through the impeller sleeve, the radial dimension of the impeller sleeve becomes inevitably large, and thus the radial dimension of the torque converter becomes large.
It is also recognized in the known automatic transaxle that the assembly and the subsequent adjustment of the driver and follower chain sprockets require skilled labour and thus are difficult since the follower chain sprocket is rotatably supported by the follower sprocket support which is different from the reaction shaft which rotatably supports the driver sprocket. If there should exist misalignment, occurrence of noise is unavoidable.
As mentioned above, the control valve assembly is arranged between the pump and the driver chain sprocket, so the axial dimension becomes large. This arrangement of the control valve assembly is an obstacle to reduction in the axial dimension.